In many technical areas, the surface structure of a component or material is an important quality feature.
There is therefore a large variety of roughness measuring devices for measuring the roughness or roughness depth of surfaces. Typically, mechanical scanning is carried out in which a probe tip is guided over the surface. The result is a height signal recorded over the tactile path, also known as a surface profile.
Skid probes 1 are known, as shown in FIG. 1 in schematic form. A skid probe 1 has a skid 2 which has a large or small radius depending on the application and which serves as a sliding element. The probe tip 4 of a probe 3 rests with the skid 2 on a surface F to be measured and measures the surface profile relative to the path of the skid 2 with the probe tip 4. During the measurement, the skid 2 follows the macroscopic unevenness of the surface F, i.e., the waviness and macroscopic shape. The probe tip 4, on the other hand, records the surface roughness with its small tip radius and detects grooves, for example, which were bridged by the skid 2, as this has a much larger effective radius. The skid 2 thus acts as a kind of mechanical high-pass filter.
From the published patent application WO 2010079019A2 (see also EP patent EP 2199732 B1) another skid probe is known. This skid probe is shown in FIG. 2A in a corresponding function view. To be able to compare the skid probe of FIG. 2A with the solution of FIG. 1, the same reference numerals were used here. The sliding element 2 is located at the extreme end of a stylus. A probe with the probe tip 4 is integrated in the stylus, wherein the distance A between the sliding element 2 and the probe tip 4 is fixed.
Another skid probe 1 is shown in FIG. 2B. The skid probe 1 of FIG. 2B is based on the basic principle of FIG. 2A. In contrast to FIG. 2A, however, the sequence of probe tip 4 and sliding element 2 is reversed. In the example shown in FIG. 2B, the probe tip 4 is in front of sliding element 2. Here too, the distance A between sliding element 2 and probe tip 4 is predetermined in a fixed manner.
Skid probes can deliver partially falsified results. This is the case, for example, if the movement of the skid 2 is superimposed constructively on the movement of the probe tip 4 and a too large output signal is supplied, or if the movements are completely or partially cancelled and a too small signal is thus supplied.
Other problems occur, for example, when measuring the surface properties of tooth flanks. On the one hand, the existing skid probes are not suitable for immersing far into the tooth gaps of small-module gears. On the other hand, sliding element 2 runs free when the tooth crest of a tooth flank is reached. As a result, the topography of tooth flanks cannot be measured close to the tooth crest. A solution according to FIG. 2A is not suitable as the probe tip 4 runs free when reaching the tooth crest. In the case of a solution according to FIG. 2B, on the other hand, the skid 2 would run free when reaching the tooth crest.
From the published patent application EP 3228974 A1 a roughness measurement probe is known, which includes a lateral skid. A corresponding roughness measurement probe 1 is shown in FIGS. 2C and 2D. FIG. 2C shows a side view and FIG. 2D shows the front area of the roughness measurement probe 1 diagonally from below. This roughness measurement probe 1 comprises a lateral skid 5 and a probe tip 4. The probe tip 4 is located in the area of the extreme end of a probe arm 6. The skid 5 is located laterally as close as possible to the probe tip 4, i.e. the skid 5 and the probe tip 4 are both in the same plane SE (cf. FIG. 2C).
Due to the very small tip radius of the probe tips 4, which are used in the previously known probe systems, these are relatively sensitive and therefore tend to wear or, if uncontrolled movements are carried out, become destroyed.
In addition, the prior known probe systems cannot be used in all situations, as they cannot be guided into corners or edges due to their size.